I also believe your Charles Sellers is a relation of mine. If it is the correct one.
My great-grandfather Robert Sellers had an uncle Charles James Sellers (born June 9th 1888), son of John Sellers and Mary Sellers (nee Boyd). John Sellers and Mary Boyd were the parents of John Sellers, my grea-great-grandfather and brother to Charles.
There was a Charles Boyd Sellers but he was my great-grandfather's brother and born April 8th 1910, so too late to be your grandfather.